The Oxford Dictionaries call a scribe as someone who copies documents in a scriptorium. In the Middle Ages, copying manuscripts was indeed part of a day’s work. It would mean that the person who wrote the original was the author.
Yet, a scribe could also be an author. To add to the confusion, most often authors and scribes were anonymous, so we never know when the manuscript is the original by an author or a copy by a scribe, until we have more copies available to us to determine which one was likely to be the original.
Furthermore, many use the term scribe interchangeably with the term author nowadays. To read more about the work of a scribe, read this post on the blog of the British Library, or this post on Medievalists.net.
Related Term: scriptorium.